[NCLUG] RAID array not started on re-boot

[Jesse Griffin]

You could possibly get away with running:

      mdadm --zero-superblock /dev/sda

After that, ensure that the RAID still looks good.  If there are problems then
you could fail sda1 out of the RAID and then add it back in, something like:

    mdadm --manage --fail /dev/md1 /dev/sda1
    mdadm --manage --remove /dev/md1 /dev/sda1
    mdadm --manage --add /dev/md1 /dev/sda1

Of course, that process will initiate a resync from the data on sdb1.  Also, if
you run into problems when re-adding sda1, then you can run the
--zero-superblock command above on sda1, then try adding it again.

Essentially, the above should give you a clean slate on sda/sda1, but may come
at the cost of rebuilding the array.  If the process works as expected, then you
could do the same steps on sdb/sdb1.

Note: I'm not guaranteeing the above by any means, but those are some ideas to
try if you are interested.


Thank you,
Jesse Griffin
tummy.com, ltd.

On 09/09/2013 02:09 PM, Kevin Olson wrote:
> As you surmised, we are using the partitions /dev/sda1 and /dev/sdb1 to
> form the array, and not the whole disks. There was an issue at some point
> in time in using the full disks, and since then we've always used the
> partitions. If one can reliably use the whole disks, I would think life
> would be easier.
> 
> It is just so strange that the "mdadm --assemble /dev/md1" worked without
> an issue, yet at boot it follows the logic you noted with the information
> from the "mdadm --misc --examine /dev/sda /dev/sdb" command.
> 
> From your explanation, I can see where the scan finds the /dev/sda and
> /dev/sdb (the whole disks) and perhaps creates the (separate) arrays from
> those on boot, due to perhaps old data. We replaced one of the disks a few
> months ago, so I presume that explains the difference in the number of
> events.
> 
> It is a bit difficult to tear the array apart at the moment, otherwise I'd
> follow your advice and zero the disks. I believe I read somewhere that in
> the /etc/mdadm.conf, it is possible to specify which devices should be
> looked at. Should I consider modifying that configuration to explicitly
> list the partitions? Would this approach make any difference on boot?
> 
> Thank you for the help!
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